There are several methods described in the chemical literature for the synthesis of diaminobenzobisthiazoles and related compounds. Various disadvantages are associated with these procedures.
French Pat. No. 1,224,183 and J. Org. Chem., 33, 2132 (1968) disclose the reaction of p-phenylenediamine, ammonium thiocyanate and bromine in acetic acid to yield diaminobenzobisthiazole compounds. The compound 2,6-diaminobenzobisthiazole is produced by means of the following illustrated reaction series: ##STR1##
Hydrolysis of 2,6-diaminobenzobisthiazole followed by acidification affords a salt of diaminobenzenedithiol (DABDT), which is useful as a comonomer in the preparation of polybenzthiazole (PBT): ##STR2##
Among the disadvantages of prior art methods for synthesizing diaminobenzobisthiazole compounds are the use of corrosive and toxic reactants such as bromine and chloroform. Any prospective large scale process for diaminobenzobisthiazole production would endeavor to avoid the use of such noxious chemicals.
An alternative route of potential interest is the synthesis of amino-substituted aromatic compounds via an electrochemical reaction mechanism.
Chemical Abstracts, Vol. 39, Col. 934 (1945) discloses a procedure for producing 2-amino-6-methylbenzothiazole from p-toluidine and ammonium thiocyanate in HCl/C.sub.2 H.sub.5 OH under electrolysis conditions.
Encyclopedia Of Electrochemistry (1964), pages 532-536, discloses the reaction of electrochemically-generated thiocyanogen with organic compounds.
There remains a need for a safe and efficient process for providing useful heterocyclic compounds such as diaminobenzobisthiazoles.
Accordingly, it is an object of this invention to provide a process for the production of diaminobenzobisthiazole compounds which does not involve the use of noxious reagents.
It is another object of this invention to provide an electrochemical process for the production of 2,6-diaminobenzobisthiazole.
Other objects and advantages of the present invention shall become apparent from the accompanying description and examples.